From hitherto, many pigments have been used as colorants for ink jet recording inks and writing instrument inks, this being because pigments are excellent in terms of water resistance, light-fastness and durability. Pigments are not soluble in water, and hence in the case of use in an ink composition, it is important for a pigment to be stably dispersed in water in the form of minute particles. From the viewpoint of making the pigment readily wettable by water, preventing settling of the pigment and so on, such an ink composition having a pigment as a colorant is generally manufactured by subjecting a mixture comprising the pigment, a liquid medium and a dispersant to dispersion treatment using a disperser or the like to prepare a pigment dispersion, and then adding various additives to the pigment dispersion as required. In this way, when manufacturing ink compositions, pigments are often used in the form of pigment dispersions, and in particular because a pigment dispersion will affect the properties of the ink composition manufactured therefrom, various art relating to pigment dispersions has been developed (see, for example, the specification of U.S. Pat. No. 5,696,182).
However, with pigment dispersions hitherto, when preparing the pigment dispersion into an ink composition, it has not been possible to simultaneously realize all of good glossiness of color images formed using the ink composition, prevention of bronzing, and good storage stability of the ink composition. That is, with ink compositions prepared from pigment dispersions hitherto, the glossiness of color images has not been sufficient, and a so-called ‘bronzing’ phenomenon has occurred in which, due to the particle size distribution of the discharged pigment, the recorded surface exhibits a bronze color depending on the viewing angle, and hence it has not been possible to realize high image quality, and moreover the storage stability of the ink composition has not been sufficient.
It is thus a problem of the present invention to provide a pigment dispersion that enables preparation of an ink composition that has excellent storage stability and is for forming color images that have excellent glossiness and for which bronzing is prevented. Moreover, it is another problem of the present invention to use this pigment dispersion to provide an ink composition that has excellent storage stability and enables formation of color images that have excellent glossiness and for which bronzing is prevented, and an ink set.